Electric discharge apparatus



June 1932- R. H. DOUGHERTY ELECTRIC DISCHARGE APPARATUS Filed NOV. 8, 1928 Inventor: Robert H. DOUghePtld,

w'm/ Hrs Attor-rweg.

Patented June 14, 1932 UNITED STATES PATENT OFFICE ROBERT E. DOUG-HEREBY, OF SOOTIA, NEW YORK, ASSIGN OR TO GENERAL ELECTRIC COIM- PANY, A CORPORATION OF NEW YORK ELECTRIC DISCHARGE APPARATUS Application filed November 8, 1928. Serial No. 318,040.

The invention relates to electric discharge apparatus, and more particularly to lar epower, high voltage tubes employed for transmitting purposes.-

Tubes of the transmitter type have heretofore been constructed in which the reentrant stem, through which the various leading-in conductors pass, is located in the neighborhood of the filament. However, it has been found that devices constructed in this manner in many instances break due to the presence of one or more minute cracks or fissures developed in the stem which allow air leakage and destruction of the vacuum. While many theories may be advanced to account for the development of these cracks, I believe that the phenomenon is the result of electrolysis which takes place about the stem under the action of the current which flows through the conductors embedded in the stem. It has further been noted that the failure of the stem is particularly pronounced and accelerated in point of time when it receives an appreciable amount of heat by radiation from the filament and other heated parts. 'While heretofore it has been 7 proposed to remove the stem a distance away from the filament to prevent the deleterious effects referred to hereinbefore, the design of tube roduced with this purpose in view has also een subject to several disadvantages. In the first place, considerable difiiculty has been experienced in the manufacture of the proposed tube, particularly in securing the proper alignment of the various electrodes and leads which in an ordinary type of power tube may extend as far as 20 to 24 inches beyond the stem support and secondly, it has also been found that because of the length and weight of the electrodes, large mechani-v cal stresses are set up in the glass about the stem support. Moreover, the mechanical arrangement of the parts was such that the stem could not readily be positioned far enough away from the filament, to present all objec-- tionable heating effect on the glass. According to the present invention, I provide a novel form of tube construction in which the stem is located remote from the heated electrodes but in which the disadvantages, re-

ductors in their proper positions within the 7 tube. This support also includes a heat barrier, for the purpose of preventing undue heating of the stem. I

Some of the objects of my invention are: to provide an inverted stem in a vacuum tube which will be inexpensive and simple to fabricate but nevertheless will have a marked degree of practicability; to move the position of the stem and press member the maximum practicable distance away from the filament and other heated elements thereby maintaining the glass portions as cool as possible; to relieve mechanical stress in the stem in the event the filament conductors are relatively long; to rigidly fix the position of the filament conductors and the filament supported therefrom, within. the envelop and in general, to increase the operating lifeand improve the design of electron discharge apparatus. Other objects and features will be apparent as the specification is perused in connection with the accompanying drawing in which Fig 1 represents an elevational view, partly in section, of a power tube which stood in the art. Within the anode member,

there is positioned a helical grid or control element 3 wound upon a suitable framework 4 and a V -shaped filament 5. The grid framework is supported from the envelop by means of a plurality of stay wires 6 which are equidistantly spaced about and secured to a grid or other insulating material secured to a centrally aligned support rod 11 fused into the inverted stem 12. The upper end of the envelop is closed by the combined stem and press structure 12 which is of the inverted type and which ispositioned as close as possibleto said end of the envelop thereby to position this glass member the maximum dis? tance away from: t-hefilament. The latter is supplied. with energy through conductors 13,.

13-which are secured in the stem 12 and terminate in flexible leads 14, 14;.

In; high-voltagetubes it is necessary to maketheinter-electrode leakage path as long,

as possible and for this reason, among others,

it; is customary to separate as far as practicable, one from the other, the various electrodes and their supports. The-long spacingv of the charged members calls for relativelylong leading-in conductors, more especially for the filament, and in the prior attempts to furnish an inverted stem, it has'been found that. the conductors secured thereto produce large mechanical stress in this member. When current is passed. through the conductors, t-he stressmay give riseto undue strain, this effect of, course, being apart: from the electrolytic. phenomenon referred to hereinbefore. Moreover, the currents passing through the conductors establish electromagnetic fieldswhich may tend tobow or displace these conductors at places intermediate the points of support thereby tending to move the filamentary members out of their respective alignedpositions. In order rigidly to fix the position of each filamentconductor, particularly the middle portion thereof, within theenvelop, I provide a heat and electrically insulating. diskv 15 of glass, lava, isolantite,

quartz'or the like which may be made of two semicircular plate members, for convenience in assembly. Extending through the thickness of the disk, there may be provided three apertures, one at the center and thBDthQISdiS- posed; diametrically oppositeone another at a distance corresponding tothe space between. the filament conductors. These apertures are of'suchsize as-snugly but sli'clably'to fit about and receive the filament conductors 1.3, 13,. ,also.the-centrally disposedrod 11 inthe manner shown in Fig. 3. The insulating'disk'15 is carried by a screw clampmember 16 which is secured to an upper clamp 17 by means of a plurality oftransversely extending'arms 18-,the; upper clamp beingsomewhat similar to the lower clamp. The disk 15 is provided with portions 19 which overhang the lower clamp member thereby the more securely to lock the disk within the clamp. The upper clamp 17 tightly embraces a cylindrical glass member 20 which is formed by tapering down a skirt or extension-portion. 21 constituted by continuing the reentrant cylinder 22 which carries the inverted stem 12. In the manufaeture of a tube such as described, it has been found preferable to form the portions 21 and 22 out of separate pieces of tubing and thento-join theirends by fusing together at a position determined, generally speaking, by the lower portion of'the'inverted stem member 12, as suggested by the line. 23 (Fig, 1 instead of providing, attheoutset, a single piece of tubing-from which. toform both of the glass portions. This mode. ofmanufacturing procedure hasithe advantage. in. that the lower extension portion 21- may be fitted in a chuck and. thetaper 20- readilyv made, without having attached. thereto the added: length, of the adjacent reentrant. portion 22. The grid clamp 7 tightly embraces the portion 21 and in order to.prevent;slippage,. theremay be provided a copper mesh between the clamp and the glass surface From the foregoing it is evident that the function of thedouble clamp arrangement 16, 1'? is to providea rigidsupport for thefilament conductors at a position intermediate the stem 12 and the filament proper thereby rigidly fixing the special. relation of these,

members and preventing undue-strain at the stem. It is also evidentthat the disk 15,,.

fromthe'filament'f'rom reachingthe inverted. stem. It is apparent that the design of the tube is marked with simplicity of manufacture and practicability, also. as offering: the greatest; practicable spacing; between the filament 5 and the stem-thereby maintaining; the latteras cool as possible under the effects ofradiatediheat. It. has, beenfoundithat atube madeinthe manner described'has-a relatively long operating life which I believe tobe due to the absence of cracksand fissures which normally would; form in the: prior stems under the-action. ofeleotrolysis or other causes,

What I claimas new and desire to-secure by Letters Patent of theUnitedStates, is:

1-. Inan electron dischargedevice, anevacuated envelop containing; a. plurality of co,- operating electrodes, saidv envelopterminating in, a hollow reentrant; portion which'is- I closed by-an inverted'stem, conductors forone 1 iii;

rality of interconnected hollow clamp members, one of said members adapted to be secured to a portion of an envelop, a body of insulating material secured Within the other clamp member and adapted to support an electrode, said material having a portion which overhangs the clamp thereby the more rigidly to be secured thereto.

3. In an electron discharge device, an evacuated envelop containing a plurality of electrodes including a filament, said envelop terminating in an inverted stem, energy supply conductors for the filament secured to said stem and a clamp positioned intermediate the length of said conductors for supporting the filament, said clamp comprising an insulating disk having apertures through Which the conductors are threaded.

4. In an electron discharge device, an evacuated envelop containing a plurality of electrodes including an electrode Which normally is heated, said envelop terminating in an inverted stem, energy supply conductors for the electrodes and a clamp positioned intermediate the length of sad conductors for supporting the electrode which is heated, said clamp comprising an insulating disk in heatshielding relation With respect to said stem.

5. In an electron discharge device, an evacuated envelope containing a plurality of cooperating electrodes, said envelope terminating in a hollow reentrant portion which is closed by an inverted stem, conductors for one of the electrodes passing through said stem, and detachable means secured to the reentrant portion for supporting said conductors intermediate their length.

In Witness whereof, I have hereunto set my hand this 7th day of November, 1928.

ROBERT H. DOUGHEBTY. 

